The interiors of commercial aircraft are typically formed with a large number of components in many shapes and forms that have both practical and aesthetic functions. Currently, the aerospace and plastics industry does not have available any clear transparent materials that will pass current Federal Aviation Administration (FAA) requirements in terms of flammability resistance properties (FAR 25.853 and Appendix F), including heat release, vertical burn, smoke emissions tests, and toxic fume emissions tests. For example, the standard test method for heat release is the Ohio State University heat release test as found in FAR 25.853-Part IV.
Transparent windows used today on commercial aircraft are typically formed of a transparent polycarbonate material having a scratch-resistant polysiloxane coating. Because these polycarbonate windows do not meet the FAA requirements for OSU heat release, exemptions have been provided by the FAA to allow their use. For airplane windows, however, the FAA exemption has limited the size of the windows so as not to impose more than the historic vertical burn flammability requirement.
It is highly desirable to increase the size of these interior windows for aesthetic purposes. In order to increase the size of the windows further, while maintaining the transparency and scratch resistance properties desired, however, it is necessary to comply with the FAA requirements for OSU heat release.